A central processing unit (CPU) is the hardware within a computer that carries out the instructions of a computer program by performing the basic arithmetical, logical, and input/output operations of the system. The form, design, and implementation of CPUs have changed over the course of their history, but their fundamental operation remains much the same.
A computer can have more than one CPU. Utilizing more than one CPU is called multiprocessing. Most CPUs are microprocessors, indicating it is contained on a single chip. Some integrated circuits (ICs) can contain multiple CPUs on a single chip. Those ICs are called multi-core processors.
An inter thread/CPU interrupt (ITI) is a special type of interrupt by which one processor may interrupt another processor in a multiprocessor system if the interrupting processor requires action from the other processor. Actions that might be requested include: (1) flushes of memory management unit caches, such as translation lookaside buffers, on other processors when memory mappings are changed by one processor; and (2) stopping when the system is being shut down by one processor.
In conventional systems ITIs can be managed using an interrupt controller. The interrupt controller can be implemented using hardware components. However, the hardware components and circuitry required to implement the interrupt controller can be complex (involving many components), costly and require a significant amount of space.
It should be noted that like reference numbers refer to like elements in the figures.